Apparatus for mapping optical elements

ABSTRACT

An apparatus for mapping an optical element, the apparatus including a light source arranged to transmit a light beam toward the optical element, a beam separator including a plurality of beam separating elements, less than all of which are identical, which are operative to separate the light beam into a corresponding plurality of light beam portions including at least first and second light beam portions which differ from one another, an optical sensing device operative to generate a light spot map including a plurality of light spots corresponding to the plurality of beam separating elements and an optical element characteristic computation device operative to derive at least one characteristic of the optical element from the light spot map and including apparatus for identifying the beam separating element corresponding to an individual spot based at least partly on differences between the at least first and second light beam portions.

FIELD OF THE INVENTION

The present invention relates to apparatus for mapping optical elementsgenerally.

BACKGROUND OF THE INVENTION

Apparatus for measuring and mapping optical elements is described in thefollowing U.S. Pat. Nos. 4,725,138; 5,083,015; 3,832,066; 4,007,990;4,824,243; and 5,287,165.

Apparatus for measuring and mapping optical elements is also describedin the following patent documents: German Democratic Republic 247,617and 213,057; Soviet Union 1,420,428 and 1,312,511; Germany 4,222,395;and in applicant's copending Israel application 110016.

A method and equipment for mapping radiation deflection by phase objectsis described in Israel Patent 61405.

A method for measuring ophthalmic progressive lenses is described in C.Castellini, F. Francini, and B. Tiribilli, "Hartmann test modificationfor measuring ophthalmic progressive lenses", Applied Optics, 1 July1994, vol. 33, no. 19, pp. 4120-4124.

Mathematical methods useful for mapping lenses are described in YogehJalurig, Computer Methods for Engineering, Ally and Bacon, Inc., page272.

The disclosures of all of the above are hereby incorporated herein byreference.

SUMMARY OF THE INVENTION

The present invention seeks to provide improved apparatus for mappingoptical elements.

The present invention relates to a system for the non-contact testing ofthe optical parameters of optical elements, in particular ophthalmicelements, both transmissive and reflective, across the entire surfacethereof, as well as to the testing of molds, mirrors, and the like.

The invention also relates to a method for the non-contact testing ofthe optical parameters of optical elements, in particular ophthalmicelements.

For the sake of simplicity, the term "optical elements" as used hereinis intended to embrace not only elements such as lenses, but also otherelements such as molds used in the production of such lenses, as well asother elements such as mirrors. Such elements include spherical andaspherical, bifocal, multi-focal and progressive lenses, as well asmolds for producing some of these lenses and, furthermore, hard and softcontact lenses.

While considerable progress has been made in the manufacturing ofsophisticated ophthalmic lenses, most of the quality control equipmenthas been lagging behind and no longer satisfies the needs of theindustry and the market.

Most of the instruments used today provide information concerning powerthat is based in a very small area of the component to be tested (3-4 mmin diameter. Furthermore, they do not provide objective results,requiring, as they do, operator decision. Also, because of theabove-mentioned, very restricted measurement area, they cannot deal withprogressive lenses, i.e., lenses with continuously changing power.

The instruments used today to analyze surface geometry are mechanicaldevices which are liable to damage highly polished surfaces (e.g.,finished lenses or molds). Testing with these instruments are verytime-consuming.

It is thus one of the objectives of the present invention to provide asystem that, within a few seconds, provides non-contact, objectivemeasurement of the optical parameters of the entire surface of anyoptical component.

It is another objective of the invention to permit measurements eitherby transmission or by reflections.

It is a still further objective of the invention to facilitateautomation of the entire measurement process.

According to the invention, the above objectives are achieved byproviding a system for the non-contact testing of optical parameters ofan optical elements, comprising a light source producing a beam of adiameter substantially covering the entire active surface of saidelement; an array of microlenses mounted at a distance from, and coaxialwith, said light source, said array being of such a size as tosubstantially cover said active surface of said element; mounting meansto mount said element to be tested in transmission, said element beinglocated between said light source and said array of microlenses; adiffusive screen for said array of microlenses, onto which to project amultiple image of said light source; an electronic camera for recordingsaid multiple image off said screen, and a computer for processing saidimage as supplied by said camera and producing a graphic and/oralphanumeric output.

The invention also provides a method for the non-contact testing of theoptical parameters of an optical element, comprising the steps ofproviding a light source adapted to produce a beam with a wave front ofa perdeterminable geometry; at least optically interposing said opticalelement to be tested between said light source and an array ofmicrolenses of a known geometry; receiving, via said array, multipleimages of said light source on a screen; recording said multiple imagesoff said screen; analyzing the geometry of said multiple images asrecorded, and comparing the geometry of said multiple images with areference pattern.

Basically, the system constitutes a wave front analyzer, measurement ofthe optical elements consisting of the analysis of the front of the waveproduced by a light source and passing through, or being reflected by,the element tested. The wave front, modified by the element, is locallysampled and geometrically analyzed by an array of microlenses, each ofwhich creates an image of light source produced on the collective imageplane located in the focal plane of the array. In this plane, a CCDcamera records the image pattern produced by the array and adata-processing subsystem produces, within a few seconds, a map of thetotal surface of the optical element tested.

If measurement of the optical element is performed by transmission, theresult is a power map of the total element area (in diopters). Ifmeasurement is carried out by reflection, the result is a topographicmap of the total element area (in millimeters).

There is thus provided in accordance with a preferred embodiment of thepresent invention a system for the non-contact testing of opticalparameters of an optical element, including a light source producing abeam of a diameter substantially covering the entire active surface ofthe element, an array of microlenses mounted at a distance from, andcoaxial with, the light source, the array being of such a size as tosubstantially cover the active surface of the element, mounting means tomount the element to be tested in transmission, the element beinglocated between the light source and the array of microlenses, adiffusive screen for the array of microlenses, onto which to project amultiple image of the light source, an electronic camera for recordingthe multiple image off the screen, and a computer for processing theimage as supplied by the camera and producing a graphic and/oralphanumeric output.

There is also provided in accordance with another preferred embodimentof the present invention a system for the non-contact testing of opticalparameters of an optical element, including a light source producing abeam of a diameter substantially covering the entire active surface ofthe element, an array of microlenses mounted at a distance from, and incoaxiality with, the element to be tested, a beam splitter mountedbetween the array of microlenses and the element to be tested inreflection, the beam splitter including substantiality equal angles withthe axis connecting the element and the array, and with axis of thelight source, a diffusive screen for the array of microlenses, ontowhich to project a multiple image of the light source, an electroniccamera for recording the multiple image off the screen, and a computerfor processing the image as supplied by the camera and producing agraphic and/or alphanumeric output.

Further in accordance with a preferred embodiment of the presentinvention the light source is provided with a collimating lens.

Still further in accordance with a preferred embodiment of the presentinvention the light source is provided with at least one condenser lens.

Additionally in accordance with a preferred embodiment of the presentinvention the light source is provided with a pin-hole apertureproducing a conical light bundle.

There is also provided in accordance with another preferred embodimentof the present invention a method for the non-contact testing of opticalparameters of an optical element, including the steps of providing alight source adapted to produce a beam with a wave front of apredeterminable geometry, at least optically interposing the opticalelement to be tested between the light source and an array ofmicrolenses of known geometry, receiving, via the array, multiple imagesof the light on a screen, recording the multiple images off the screen,analyzing the geometry of the multiple images as recorded, and comparingthe geometry of the multiple images with a reference pattern.

Further in accordance with a preferred embodiment of the presentinvention the method includes the step of generating graphic and/oralphanumeric results.

There is also provided in accordance with another preferred embodimentof the present invention apparatus for mapping an optical element, theapparatus including a light source arranged to transmit a light beamtoward the optical element, a beam separator including a plurality ofbeam separating elements operative to separate the light beam into acorresponding plurality of light beam portions, an optical sensingdevice operative to generate a light spot map including a plurality oflight spots corresponding to the plurality of beam separating elements,and an optical element characteristic computation device operative toderive at least one characteristic of the optical element from the lightspot map and including apparatus for identifying the beam separatingelement corresponding to an individual spot based at least partly oninformation other than the location of the spot.

Further in accordance with a preferred embodiment of the presentinvention the light spot map includes a digital light spot map.

Still further in accordance with a preferred embodiment of the presentinvention the light spot map includes an analog light spot map.

Additionally in accordance with a preferred embodiment of the presentinvention the deflector includes an LCD (liquid crystal device).

Moreover in accordance with a preferred embodiment of the presentinvention the deflector includes an array of microlenses.

Further in accordance with a preferred embodiment of the presentinvention the deflector includes a hole plate.

Still further in accordance with a preferred embodiment of the presentinvention the optical sensing device includes a CCD camera.

Additionally in accordance with a preferred embodiment of the presentinvention the optical sensing device includes an IR camera.

Moreover in accordance with a preferred embodiment of the presentinvention the optical sensing device includes a photographic film.

Further in accordance with a preferred embodiment of the presentinvention the optical sensing device includes a PSD (position sensordetector).

Still further in accordance with a preferred embodiment of the presentinvention the light source includes a point source.

Additionally in accordance with a preferred embodiment of the presentinvention the light source includes a coherent light source.

Moreover in accordance with a preferred embodiment of the presentinvention the coherent light source includes a laser source.

Further in accordance with a preferred embodiment of the presentinvention the light source includes a noncoherent light source.

Still further in accordance with a preferred embodiment of the presentinvention the noncoherent light source includes one of the following: atungsten light source, and a halogen light source.

Additionally in accordance with a preferred embodiment of the presentinvention the apparatus for identifying also employs informationregarding the location of the spot to identify a beam separating elementcorresponding to an individual spot.

Moreover in accordance with a preferred embodiment of the presentinvention the light source includes a parallel light source operative totransmit parallel light toward the optical element.

Further in accordance with a preferred embodiment of the presentinvention the light source includes a convergent light source operativeto transmit converging light toward the optical element.

Still further in accordance with a preferred embodiment of the presentinvention the light source includes a divergent light source operativeto transmit diverging light toward the optical element.

Additionally in accordance with a preferred embodiment of the presentinvention the computation device is operative to derive at least onelocal characteristic of the optical element.

There is also provided in accordance with another preferred embodimentof the present invention a method for mapping an ophthalmic elementincluding illuminating an ophthalmic element, providing a plurality ofbeam separating elements operative to separate a light beam into acorresponding plurality of light beam portions, generating a digitallight spot map including a plurality of light spots corresponding to theplurality of beam separating elements, and deriving at least oneophthalmic element characteristic.

Further in accordance with a preferred embodiment of the presentinvention the deriving step includes deriving at least one localophthalmic element characteristic.

Still further in accordance with a preferred embodiment of the presentinvention the ophthalmic element includes an ophthalmic lens.

Additionally in accordance with a preferred embodiment of the presentinvention the ophthalmic element includes an ophthalmic mold.

Moreover in accordance with a preferred embodiment of the presentinvention the ophthalmic lens includes a contact lens.

Further in accordance with a preferred embodiment of the presentinvention the contact lens includes a hard contact lens.

Still further in accordance with a preferred embodiment of the presentinvention the contact lens includes a soft contact lens.

Additionally in accordance with a preferred embodiment of the presentinvention the soft contact lens is immersed in a solution.

Moreover in accordance with a preferred embodiment of the presentinvention the ophthalmic lens includes an intraocular lens.

There is also provided in accordance with another preferred embodimentof the present invention apparatus for mapping an ophthalmic lensincluding a light source arranged to transmit light toward theophthalmic lens, a beam separator including a plurality of beamseparating elements operative to separate a light beam into acorresponding plurality of light beam portions, an optical sensingdevice operative to generate a digital light spot map including aplurality of light spots corresponding to the plurality of beamseparating elements, and an ophthalmic characteristic map generatingdevice operative to generate a map of an ophthalmic characteristic ofthe ophthalmic lens based on the light spot map.

Further in accordance with a preferred embodiment of the presentinvention the ophthalmic characteristic map includes an astigmatism map.

Still further in accordance with a preferred embodiment of the presentinvention the ophthalmic characteristic map includes an axis map.

Additionally in accordance with a preferred embodiment of the presentinvention the ophthalmic characteristic map includes a tilt map.

Moreover in accordance with a preferred embodiment of the presentinvention the ophthalmic characteristic map includes a curvature radiusmap.

There is also provided in accordance with another preferred embodimentof the present invention a method for mapping an IR optical elementincluding illuminating an IR optical element, providing a plurality ofbeam separating elements operative to separate a light beam arrivinginto a corresponding plurality of light beam portions, generating adigital light spot map including a plurality of light spotscorresponding to the plurality of beam separating elements, and derivingat least one IR optical element characteristic.

There is also provided in accordance with another preferred embodimentof the present invention apparatus for mapping an optical elementincluding a light source arranged to transmit light toward the opticalelement, a beam separator including a plurality of beam separatingelements operative to separate a light beam into a correspondingplurality of light beam portions, an optical sensing device operative togenerate a digital light spot map including a plurality of light spotscorresponding to the plurality of beam separating elements, and anaberration polynomial computation device operative to derive anaberration polynomial characterizing the optical element from the lightspot map.

Further in accordance with a preferred embodiment of the presentinvention the apparatus also includes a beam splitter positioned betweenthe light source and the optical element which is operative to split thelight beam returning from the optical element toward the optical sensingdevice.

Still further in accordance with a preferred embodiment of the presentinvention the optical sensing device is on one side of the opticalelement and the light source is on the other side of the opticalelement.

There is also provided in accordance with another preferred embodimentof the present invention apparatus for mapping an optical element, theapparatus including a light source arranged to transmit a light beamtoward the optical element, a beam separator including a plurality ofbeam separating elements operative to separate a light beam arrivingfrom the light source into a corresponding plurality of light beamportions before impingement of the light beam on the optical element, anoptical sensing device operative to generate a digital light spot mapincluding a plurality of light spots corresponding to the plurality ofbeam separating elements, and an optical element characteristiccomputation device operative to derive at least one characteristic ofthe optical element from the light spot map.

Further in accordance with a preferred embodiment of the presentinvention the at least one characteristic of the optical elementincludes at least one characteristic of only one surface of the opticalelement.

Still further in accordance with a preferred embodiment of the presentinvention the at least one ophthalmic element characteristic includes atleast one ophthalmic characteristic of only one surface of the opticalelement.

Additionally in accordance with a preferred embodiment of the presentinvention the at least one IR optical element characteristic includes atleast on IR optical element characteristic of only one surface of the IRoptical element.

Moreover in accordance with a preferred embodiment of the presentinvention the aberration polynomial characterizes only one surface ofthe optical element.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated from thefollowing detailed description, taken in conjunction with the drawingsin which:

FIG. 1 represents the array of focal points as produced by plane wavefront passing through an array of microlenses;

FIG. 2 represents the image produced by the array of microlenses of FIG.1;

FIG. 3 shows the effect of introducing a positive lens between the lightsource and the array of microlenses;

FIG. 4 is the image produced by the setup of FIG. 3;

FIG. 5 shows the effect of introducing a negative lens into the setup;

FIG. 6 is the image produced by the setup of FIG. 5;

FIG. 7 represents a cylindrical lens;

FIG. 8 is the image pattern of the lens of FIG. 7;

FIG. 9 shows a bifocal lens;

FIG. 10 presents the image pattern of the lens of FIG. 9;

FIG. 11 presents a progressive lens;

FIG. 12 represents the image pattern of the lens FIG. 11;

FIG. 13 illustrates a setup of the system in which an optical componentis tested in transmission;

FIG. 14 represents a setup in which the front surface of the element istested in reflection;

FIG. 15 illustrates the testing of the front surfaces of a progressivelens in transmission; FIG. 16 is a cylindrical map of a progressivelens, including a power scale relating the different shadings to localpower;

FIG. 17A is a simplified partly pictorial, partly block diagramillustration of apparatus for mapping an optical element, the apparatusconstructed and operative in accordance with an alternative preferredembodiment of the present invention;

FIG. 17B is a simplified block diagram of the apparatus of FIG. 17A.

FIG. 18A is a simplified flow chart illustrating the operation of theoptical element computation device 96 of FIG. 17B,

FIG. 18B is a simplified pictorial diagram illustrating calibrationspots produced during step 105 of FIG. 18A;

FIG. 18C is a simplified pictorial diagram illustrating test spotsproduced during step 110 of FIG. 18A;

FIG. 19 is a simplified flow chart illustrating the operation of step112 of FIG. 118A;

FIGS. 20A and 20B are simplified pictorial illustrations of a result ofstep 140 of FIG. 19;

FIG. 21-28 are simplified partly pictorial, partly block diagrams ofeight different alternative configurations of the apparatus of FIGS. 17Aand 17B; and

FIG. 29 is a simplified pictorial illustration of a cylinder map aprogressive lens, as produced by the apparatus of FIG. 17A and 17B.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, there is seen in FIG. 1 a microlens array2 with lenses of a diameter d. When, as shown, the array 2 is impactedby a plane wave front, the lenses focus at f1, f2 . . . fn in thecollective focal plane, with the pitch p of the foci f in this casebeing p=d. If a screen were mounted in the focal plane, the multipleimages of the light source (not shown) producing that wave front wouldappear as in FIG. 2, with the pitch in both directions being p.

When, as in FIG. 3, a positive lens L+ is interposed between the lightsource and the array 2, the above multiple image, produced on a screen4, would appear as in FIG. 4, but with p<d.

Conversely, with a negative lens L- interposed between light source andarray 2 as shown in FIG. 5, the image would appear as in FIG. 6, withp>d.

As will be explained in detail further below, the image on screen 4 isrecorded by a CCD camera and processed by a computer.

FIGS. 7-12 represent various special lenses and the specific multipleimages produced by them with the system according to the invention.

FIG. 7 represents a cylindrical lens having both an X and a Y axis. Inthe image of FIG. 8 as produced by array 2 (not shown), X<Y.

FIG. 9 shows a bifocal lens LBF having a focal length f1 in its upperpart and a focal length f2 in its lower part. The image pattern producedby array 2 is shown in FIG. 10. It is seen that the density of the imagepoints in the upper part of the lens is lower than that in the lowerpart.

The lens in FIG. 11 is a so-called progressive lens Lprog, the focallength of which varies across the surface thereof. This is clearly shownin the image pattern of FIG. 11 where the zones of different power andthe transitions between them appear as image points of differentdensities.

FIGS. 13-15 schematically represent the system according to theinvention.

In FIG. 13 there is seen a light source 6 which is preferably white andneed not be coherent, although a HeNe laser (0.6 microns) can be used. Acollimator lens 8 is provided to produce a beam having a plane wavefront. Further seen is the microlens array 2. The array used in anexperimental version of the system had the following specifications,which should be seen by way of example only:

    ______________________________________                                        Lens diameter        1 mm                                                     Focal length of lenses                                                                             5-10 mm                                                  Number of lenses     40 × 40 = 1600                                     Pitch of lenses      3 mm                                                     Overall size of array                                                                              .sup.˜ 120 mm                                      ______________________________________                                    

Also seen is a diffusive screen 4 on which appear the multiple images oflight source 2 as modified by the lens to be tested LT. These images arerecorded by a CCD camera 10, the output of which is transferred tocomputer 12, where the images are processed. The system of FIG. 13clearly works by transmission.

A reflective system according to the invention is schematicallyillustrated in FIG. 14. Such a system is intended for analyzing onesurface only of a tested lens of when elements are to be tested.

There are seen in FIG. 14 a light source 6, a condenser lens 14, a beamsplitter 16, the microlens array 2 and its screen 4, a CCD camera 10 anda computer 12. The beam from light source 6 is seen to fall onto beamsplitter 16, onto array 2, producing the already-discussed imagepattern. This pattern is recorded by CCD camera 10 and is analyzed incomputer 12.

It will be noticed that, in this case, the beam is not parallel as inthe previous embodiment, but converging. This is done in order to reducethe size of the lens array required, since the convex surface of thetest element would turn a parallel beam into a diverging one, whichwould demand a much larger array 2.

The embodiment of FIG. 15 enables the progressive surface of aprogressive lens to be tested in transmission rather than reflection, aswas the case in FIG. 14.

There is seen in FIG. 15 a high-intensity light source 6 with a pin-holeaperture 18. The progressive lens Lprog is mounted at a distance r fromthe pin hole, where r is the radius of curvature of the spherical rearsurface SSPH and will therefore pass the rear surface SSPH without beingrefracted. While a certain amount of energy will be reflected back intothe pin hole 18, the main portion of the light will be refracted at thecontinuous front surface SCONT.

Image processing, carried out in the computer with the aid of anacquisition card, includes the following steps:

1) Assessment of all image-point locations at pixel accuracy.

2) Determination of the centroid of all point at sub- pixel accuracy(1/10-1/30 pixel) by modellization of the Gaussian spot and thuslocating the energetic center.

3) Determination of the shift of the centroid by comparison with areference image.

4) Converting the above shift into a topographical map of the lens.

For deeper analysis, that is, for analysis of the common aberrations,use is made of the polynomial of Zernike, whereby it is possible todetermine the different optical aberrations in the order of thepolynomial with the coefficients of each of the terms of the polynomialtaken in a certain order, indicating the contribution to total lensimperfection of a given aberration.

The output of the system as working in transmission will be atopographical cylindrical map, as shown in FIG. 16. Unlike the presentillustration, which is shaded to indicate coloring, the real map iscolored and so is the associated power scale, which relates thedifferent shadings to local power. It is also possible to calculate themaximum power, the axis and the prism of the tested lens.

Output of the system as working in reflection will be in the form of aphysical topographical map, colored as the map of FIG. 16, but with thecolor differences indicating differences in height between thetopographical outlines, or a table which will give on each x,y positionon the lens the real height of the surface.

The system according to the invention is easily automated by theprovision of a robot arm which takes the appropriate mount and,according to the test results, separates the serviceable from the faultylenses.

Reference is now made to FIGS. 17A and 17B. FIG. 17A is a simplifiedpartly pictorial, partly block diagram illustration of apparatus formapping an optical element, the apparatus constructed and operative inaccordance with an alternative preferred embodiment of the presentinvention, while FIG. 17B is a simplified block diagram of the apparatusof FIG. 17A. The configuration of FIG. 17A comprises a lighttransmission configuration using a parallel beam.

Shown in FIG. 17A is an optical element 87, which is to be tested by theapparatus of FIGS. 17A and 17B. The optical element 87 may be any of anumber of different kinds of optical element, including an ophthalmic ornon-ophthalmic optical element; a mold; or a lens of any of a number oftypes, including an ophthalmic lens, a hard or soft contact lenspossibly immersed in a solution, or an intraocular lens. It isappreciated that many other types of optical element may also be used.

The apparatus of FIGS. 17A and 17B includes a light source 90, whichmay, for example, generally be either a coherent or a non-coherent lightsource, including: a laser, such as a diode laser; a white light source,such as a halogen light; an IR (infrared) source; or a tungsten lightsource. Typically, a halogen light with a parabolic reflector may beused as, for example, item 7106-003 commercially available from WelchAllyn, 4619 Jordan Road, P.O. Box 187, Skansateles Falls, N.Y.13153-0187, USA. In the case where the optical element 87 is an IRoptical element, an IR source is preferred.

The apparatus of FIGS. 17A and 17B also includes a beam separator 92,which may be, for example, one of the following:

an array of microlenses, such as, for example, an array of 100×100microlenses, typically equally spaced, each of 1.0 mm diameter and focallength of 50 mm, commercially available from Visionix, Ltd., 21 VaadHaleumi, Jerusalem, Israel;

a hole plate, such as, for example, a plate containing an array of 40×40holes, typically equally spaced, each of 300 micron diameter, interholedistance 2.5 mm, commercially available from Visionix, Ltd., 21 VaadHaleumi, Jerusalem, Israel; or

an LCD (liquid crystal device).

Generally, an array of microlenses is preferred, although a hole platemay typically be used because an array of microlenses is often moreexpensive.

In any case, one of the plurality of microelements of the beam separator92 as, for example one of the microlenses or one of the holes, isreplaced with a non-light-transmitting material, so that no beam oflight is produced by the replaced microlens or hole. Preferably, thereplaced microlens or hole is located generally in the center of thearray of microlenses or holes and is referred to hereinbelow as a"missing element".

The apparatus of FIGS. 17A and 17B also includes an optical sensingdevice 94. Typically, the optical sensing device comprises a screen 88,shown in FIG. 17A, upon which light beams may be projected. The screen88 is typically an optical matte screen. The optical sensing device 94typically also comprises a camera 89, shown in FIG. 17A, such as, forexample:

a CCD camera such as a Burle model TC65 CCD camera, commerciallyavailable from Maagal Sagour Ltd., 11 Hosheha St., Bnei Berak 51364,Israel;

an IR camera, preferred when an IR light source is used;

photographic film; or

a PSD (position sensor detector), such as a UTD model PDH.4 availablefrom UDT sensors, Inc., 12525 Chadron Ave., Hawthorne, Calif. 90250,USA.

Generally, a CCD camera is preferred.

The apparatus of FIGS. 17A and 17B also includes an optical elementcomputation device 96 which may be, for example, an appropriatelyprogrammed IBM compatible personal computer equipped with a 66 MHz 80486processor and an image processing card with acquisition ability, such asa frame grabber card with analog to digital termination, availablecommercially from CEFAR Ltd., Har Hotsvim, Phasecom Building, Jerusalem,Israel.

In the case where photographic film is used in the optical sensingdevice 94, within the camera 89, the film must be examined afterdeveloping and data derived from the film must be manually orautomatically input to the optical element computation device 96. Inthis case, acquisition capability is not required in the imageprocessing card referred to above. In the case of photographic film, thesensed data is termed analog data, while in the case of the otherexamples of a camera given above, the sensed data is termed digitaldata.

Reference is now made to FIG. 18A which is a simplified flow chartillustrating the operation of the optical element computation device 96of FIGS. 17A and 17B. The method of FIG. 18A includes a preferred set ofsteps to be taken by the user in order to operate the apparatus of FIGS.17A and 17B. The method of FIG. 18A preferably includes the followingsteps:

STEP 100: Parameters. The user may optionally input control parametersthat govern the method of FIG. 18A. Parameters may, for example,comprise the following:

integration number, indicating how many times an image of the opticalelement 87 is to be acquired;

optical element parameters, typically comprising:

sagittal;

diameter; and

refractive index and, in the case where the optical element 87 issubmerged in a liquid, the refractive index of the liquid;

structural parameters of the apparatus, typically comprising:

maximum number of microelements, such as microlenses or holes, along anaxis of the beam separator 92;

distance between microelements, such as microlenses or holes, along anaxis of the beam separator 92;

distance between the beam separator 92 and the screen 88 typically foundin optical sensing device 94; and

distance between the optical element 87 and the beam separator 92;

erosion parameters, described in detail below with reference to FIG. 19,including window size along both axes, and erosion threshold;

output parameters, typically comprising:

type of map, such as sphere, cylinder, astigmatism, tilt, curvatureradius, or axis;

step of the measurement;

scaling of output.

STEP 105: Calibration. A measurement is taken without including theoptical element 87 in the apparatus.

Reference is now additionally made to FIG. 18B, which is a simplifiedpictorial diagram illustrating calibration spots produced during step105 of FIG. 18A. FIG. 18B comprises a plurality of calibration spots 97.A relatively small number of calibration spots 97 is shown in FIG. 18Bfor illustrative purposes. Generally, the number of test spots is equalto the number of microelements in the beam separator 92. For example, inthe case where the beam separator 92 comprises a 100×100 microlens,there are generally 10,000 calibration spots 97.

The location of the calibration spots 97 is recorded in memory as thebasis for future measurement. Typically, the distance between any twoadjacent calibration spots 97 in the horizontal direction issubstantially the same as the distance between any other two adjacentcalibration spots 97 in the horizontal direction, and similarly in thevertical direction. This is because, as explained above with referenceto FIGS. 17A and 17B, the distance between elements of the beamseparator 92 is typically substantially equal. Nevertheless, smallvariations tend to make the spacing of the calibration spots 97 slightlyuneven. Therefore, the horizontal and vertical positions of each of thecalibration spots 97 is stored for use in future computations.

Each of the calibration spots 97 is assigned a unique label, as, forexample, an integer. The label of each of the test spots 97 is storedfor future computation

STEP 110: Measurement. The test optical element is inserted as shown inFIG. 17A. Reference is now additionally made to FIG. 18C, which is asimplified pictorial diagram illustrating test spots produced duringstep 110 of FIG. 18A. FIG. 18C comprises a plurality of test spots 98.It will be seen that the tests spots 98 are in different positions thanthe corresponding calibration spots 97 of FIG. 18B. The positions aredifferent because the optical element 87 inserted in the light paths hasrefracted or reflected the light beams so that the light beams impingeon different locations, thus causing the test spots 98 to be indifferent positions than the calibration spots 97.

Measurement comprises the following steps 112 and 114:

STEP 112: Image processing: the positions of the test spots 98 areacquired and processed to determine which of the calibration spots 97 isassociated with each of the test spots 98, and thereby to determinewhich microelement of the beam separator 92 is associated with each ofthe calibration spots 97 and each of the test spots 98. Step 112 isdescribed in more detail below with reference to FIG. 19.

STEP 114: The optical characteristics of the test optical element arecomputed, preferably by using the following equations. In equations1-18b , discussed below, the following symbols are used:

i, j: identifying numbers of calibration spots 97 and test spots 98;

x, y: Cartesian positions of calibration spots 97;

x', y': Cartesian positions of test spots 98;

X, Y: Cartesian distances between two spots;

D: distance between the beam separator 92 and the screen.

Equations 1 and 2, found below, define computation of X and Y.

Equations 3a and 3b, found below, define computation of the displacementbetween one of the calibration spots 97 and the corresponding test spot98.

Equations 4a and 4b, found below, define computation of the displacementof a given pair of associated spots 97 and 98 and the displacement ofanother pair of associated spots 97 and 98, thus defining a measure ofdensity.

Equations 5-8, found below, define values used in subsequent equations,where the subscripts "12"and "13" define the "i,j-values" of therespective displacements.

Equation 9a, found below, defines the local maximum power of the opticalelement.

Equation 9b, found below, defines the local minimum power of the opticalelement.

Equation 9c, found below, defines the local cylindrical surface of theoptical element.

Equation 9d, found below, defines the local average power of the opticalelement.

Equations 10a-10d, found below, define values used in equation 11.

Equation 11, found below, defines the local axis of the optical element.

Equations 12a and 12b are described below, with reference to FIG. 19.

The above computations, explained with reference to equations 1-11,comprise a computation of a numerical topography of the power of thelens. Alternatively, an aberration polynomial such as the Zernikepolynomial, which is well known in the art and may be preferred byopticians, may be used. Alternatively, another appropriate aberrationpolynomial may be used.

Equation 13a, found below, defines the Zernike polynomial. A best fitbetween the numerical data and the Zernike polynomial is computed, usingmethods well known in the art. A typical method to fit the data to theZernike polynomial is the Gaussian method, described in Yogeh Jalurig,Computer Methods for Engineering, Ally and Bacon, Inc., page 272.

Alternatively or additionally, it is possible to compute a radius ofcurvature map for either of the two surfaces of the lens, or of bothsurfaces separately. The configurations of FIGS. 22 and 23, referred tobelow, are particularly suitable for this purpose. Two measurements areperformed, with two different positions of the screen 88. For eachposition, computations similar to those described above with referenceto Equations 1-11 are performed.

First, the computations of Equations 1-3, described above, are performedfor each position of the screen 88. Then, for each position of thescreen 88, the following computations are performed.

For each of the test spots 98 on the screen 88 in the first position,the corresponding test spot on the screen 88 in the second position isidentified, as explained above in step 112 and below with reference toFIG. 19, by relating to the corresponding calibration positions. The twocorresponding test spots 98 define a straight line which intersects withthe optical element 87 on its inner surface, where the inner surface isdefined as the surface closest to the screen 88.

Generally, the radius of curvature of one of the two surfaces of theoptical element 87 is given in order to simplify computation of thecharacteristics of the other surface. This simplifying assumption ismade because, typically, progressive lenses are sphero-cylindrical onone surface, the surface of given curvature, and are of complex shape onthe other surface, the surface to be measured. Alternatively, theoptical element 37 may have only one optical surface as, for example, inthe case of a mirror. By way of example, the present discussion willassume that the radius of curvature of the inner surface is alreadyknown. It is appreciated that similar computations may be performed ifthe radius of curvature of the outer surface is already known.

Equation 13b, found below, expresses Snell's Law. Equation 13b is usedto find the perpendicular to the outer surface of the optical element 87which intersects the position of the associated microelement of the beamseparator 92, as is known in the art.

Equations 14a-14e, found below, are used to compute the direction andthe derivative of the perpendicular in three dimensions.

Equations 15a-16b, found below, define values used in Equations 17-18b.

Equation 17, found below, defines the minimum and maximum local power,k₁ and k₂, respectively.

Equation 18a, found below, defines the average power.

Equation 18b, found below, defines the cylinder power.

It is appreciated that other lens characteristics, such as axis, tilt,and coma, may also be computed with appropriate equations.

Equations 1-18b, referred to above, are as follows:

    X.sub.ij =x.sub.i -x.sub.j                                 (1)

    Y.sub.ij =y.sub.i -y.sub.j                                 (2)

    Δx.sub.i =x.sub.i -x.sub.i                           (3a)

    Δy.sub.i =y.sub.i -y.sub.i                           (3b)

    ΔX.sub.ij =Δx.sub.i -Δx.sub.j            (4a)

    ΔY.sub.ij =Δy.sub.i -Δy.sub.j            (4b)

    A=ΔX.sub.12.ΔY.sub.13 -ΔX.sub.13.ΔY.sub.12(5)

    B=X.sub.12.ΔY.sub.13 +Y.sub.13.ΔX.sub.12 -Y.sub.12.ΔX.sub.13 -ΔY.sub.12                (6)

    C=X.sub.12.Y.sub.13 -X.sub.13.Y.sub.12                     (7)

    d=B.sup.2 -4AC                                             (8)

    Fmax=Z=max(((B+d)/2A).D; ((B-d)2A).D)                      (9a)

    Fmin=min(((B+d)/2A).D; ((B-d)2A).D)                        (9a)

    Cyl=Fmax-Fmin                                              (9c)

    Sph(av)=(Fmax+Fmin)/2                                      (9d)

    x.sub.mi =x.sub.i +Δx.sub.i.Z/D                      (10a)

    y.sub.mi =y.sub.i +Δy.sub.i.Z/D                      (10a)

    α=x.sub.m2 -x.sub.m1                                 (10c)

    β=y.sub.m2 -y.sub.m1                                  (10d)

    Axe(rad)=Arctg(β/α)                             (11) ##EQU1##

    n.sub.1 Sin (θ.sub.1)=n.sub.2 Sin (θ.sub.2)    (13b)

    f.sub.x =.sub.cx.sup.cz                                    (14a)

    f.sub.y =.sub.cy.sup.cx                                    (14b)

    f.sub.xx =.sub.cx.spsb.2.sup.c.spsp.2.sup.z                (14c)

    f.sub.yy =.sub.cy.spsb.2.sup.c.spsp.2.sup.z                (14d)

    f.sub.xy =.sub.cxcy.sup.c.spsp.2.sup.z                     (14e)

    E=1+f.sub.x.sup.2                                          (15a)

    F=f.sub.x.f.sub.y                                          (15b)

    G=1+f.sub.y.sup.2                                          (15c) ##EQU2##

    U=E.f.sub.yy +G.f.sub.xx -2f.sub.x.f.sub.y.f.sub.xy        (16a) ##EQU3##

    P=.sub.2.sup.(n-1) (K.sub.1 =k.sub.2)                      (18a)

    A=(n-1)(k.sub.1- k.sub.2)                                  (18b)

STEP 115: Topography. A report of the characteristics of the opticalelement 87, such as a lens, is computed and output to the user. Thereport may be any of a number of reports representing thecharacteristics of the lens as, for example: a map of the power of thelens; a map of the cylinder of the lens; a map of the axis of the lens;a 3-dimensional wire frame map of the lens; a cross-section of the lensin any direction; a map of the radius of curvature of the lens; a map ofdifferences between the test optical element and a reference opticalelement, in which case characteristics of a previously measuredreference optical element are stored for use in computing the map ofdifferences; an indication of the quality of the lens; an indication ofacceptance or rejection of the lens according to predefined criteriachosen by the user.

Reference is now made to FIG. 19 which is a simplified flow chartillustrating the operation of step 112 of FIG. 18A. The method of FIG.19 preferably includes the following steps:

STEP 120: Acquisition. The gray levels of each pixel in the image arecaptured by the optical sensing device 94 and stored in memory by theoptical element computation device 96. Preferably, a two-dimensionalarray of gray scale values is stored. The size of each pixel determinesthe precision of the measurement. An array of 512×512 pixels ispreferred. Preferably, 256 gray levels are used, but alternativelyanother number of levels may be used.

STEP 130: Erosion. The two dimensional array of gray scale values storedin step 120 is examined in order to find the maximum brightness valuefor each test spot 98.

The array of pixels is examined by passing a two-dimensional window overthe array and examining the pixels within the two-dimensional window.Preferably, the size of the window is large compared to the size of anindividual spot and small compared to the distance between spots.Generally, the size of an individual spot and the distance between spotsare known in advance as parameters of the system, particularly of thebeam separator 92, as determined in step 105, described above. Ifnecessary, the size of the window may be varied in step 100, describedabove.

The window passes over the array, moving one pixel at a time, so thatthe window visits each possible location in the array. At each location,a function of the gray scale values of all of the pixels within thewindow is computed. Preferably, the function is the local maximum over athreshold, typically the erosion threshold supplied in step 100 of FIG.18A. The computed function value represents the local maximum ofbrightness.

As the window passes over the array, the local maxima of all windowlocations which represent maxima of brightness according to the computedfunction are stored in memory by computation device 96.

STEP 140: Grid computation.

Reference is now additionally made to FIGS. 20A and 20B, which aresimplified pictorial illustrations of a result of step 140 of FIG. 19.FIG. 20A shows the results as applied to an array of calibration spots97, and FIG. 20B shows the result as applied to an array of test spots98. The illustration of FIG. 20B shows an example of a grid generatedaccording to the method of step 140, connecting all of the test spots98.

In order to compute the optical characteristics of the test opticalelement, it is necessary to determine, for each test spot 98, which isthe corresponding calibration spot 97, that is, the calibration spot 97produced by the same light beam which produces the individual test spot98.

The array of locations of maximum, brightness computed in step 130 isexamined, beginning at the center of the array, thereof. A gridconnecting the locations of maximum brightness is created as follows:

The location of the missing microelement is first determined. For thesake of computation, it is assumed that any group of four calibrationspots 97 or four test spots 98, arranged roughly in the shape of arectangle, are roughly equally spaced. The calibration spots 97 and thetest spots 98 are examined to find a place where there are two adjacentcalibration spots 97 or test spots 98 at significantly greater distancethan the generally equal distance, as for example 25% farther. Themissing spot is taken to be between the spots which are at significantlygreater distance, as shown for example in FIGS. 20A and 20B. Preferably,the missing spot is located by linear interpolation between thelocations of the four closest spots 97 or 98.

The correspondence between the calibration spots 97 and the test spots98 is then identified as follows:

Begin at the location of the missing microelement and associate thelocation of the missing spot of the calibration spots 97 with thelocation of the missing spot of the test spots 98;

For each location of maximum brightness of the test spots 98, thenearest eight locations of maximum brightness of the test spots 98 areidentified;

Similarly, for each location of maximum brightness of the calibrationspots 97, the nearest locations of maximum brightness of the calibrationspots 97 are identified;

The eight calibration spots 97 and the geometrically corresponding eighttest spot 98 found in the previous two steps are identified asassociated spots, and each of the eight test spots 98 is assigned alabel corresponding to the label of the associated calibration spot 97;and

an indication is stored in memory of the computing device 96,representing lines connecting, horizontally and vertically, the currentlocation and the eight nearest locations, of the calibration and testspots, as seen in FIGS. 20A and 20B.

The test spots 98 are thus identified relative to the calibration spots97 by information other than the location of an individual test spot 98.

One of the nearest locations becomes the new current location so thatthe next nearest location can be identified, excluding any locationsalready identified. Any appropriate method may be used to traverse thelocations in choosing the new current location, so that all locationsare eventually traversed. Preferably, a method which optimizes searchtime is used. One example of a preferable method is a follows:

begin in the center of the image and choose a starting test spot 98 andprocess the chosen spot;

identify the four nearest neighbors of the test spot 93 in thehorizontal and vertical directions;

choose one of the four nearest neighbors as the next spot and processthe new chosen spot;

repeat the identify and choose steps.

It is appreciated that many other search methods may be used.

It will be appreciated that the above method associates each of the testspots 98 with the corresponding calibration spot 97 defines a gridconnecting all of the test spots 98. Also, since the location of themissing microelement in the beam separator 92 corresponds to the missingspots of the calibration spots 97 and the test spots 98, the abovemethod also associates each of the test spots 98 and each of thecalibration spots 97 with the corresponding microelement in the beamseparator 92 which produced said spots.

In case not all of the test spots are connected, parameters may bealtered as described above in step 100 and the entire process may beperformed again.

STEP 150: Centers computation. The center of brightness for each of thetest spots 98 is computed with subpixel precision. The center ofbrightness may not be in the same location as the maximum computed abovein step 130, typically due to quantization, noise, or other effectswithin the optical sensing device 94, with the maximum brightness beinglocated off-center.

Preferably, the center of brightness is computed as follows. For centerof brightness computation, a window centered around each brightnessmaximum for each of the test spots 98 is defined. The center ofbrightness window is similar to that described in step 130 butpreferably of a size equal to the distance between two neighboringbrightness maxima as computed in step 130. Within the window, the centerof brightness coordinate is computed with subpixel precision usingEquations 12a and 12b, referred to above, where the function I(i,j) isthe gray value of the spots i,j. The center of gravity is taken as theposition of the test spot 98.

Alternatively, in the case of a non-symmetrical distribution of light, asymmetrical polynomial such as a Bessel function or a Gaussian function,or a non-symmetrical function such as a Ksi distribution, may be chosen,and the best fit of the data to the chosen function may be computed. Theposition of spot 98 is defined as the x=0 and y=0 coordinate positionsof the function. While this method may produce a precise result, thecomputations tend to be time consuming.

Reference is now made to FIGS. 21-28, which are simplified partlypictorial, partly block diagrams of eight different alternativeconfigurations of the apparatus of FIGS. 17A and 17B.

FIG. 21 shows a light transmission configuration using a spherical beamof light. The spherical beam may be either convergent or divergent.Preferably, the radius of curvature of the spherical beam isapproximately the same as the radius of curvature of one of the twosurfaces of the optical element 87. This is preferable because a beamwith said radius of curvature will be generally unaffected by passingthrough the surface of the optical element 87 with a correspondingradius of curvature. A beam with such a radius of curvature is thuspreferable for measuring only one surface of the optical element 87,namely the surface with a different radius of curvature.

Alternatively, preferable results in measuring an optical element 87with high divergence may be obtained using a convergent beam, whilepreferable results in measuring an optical element 87 with highconvergence may be obtained using a divergent beam.

FIG. 22 shows a light transmission configuration using a parallel beam.The configuration of FIG. 22 comprises two screens 88, with the beamseparator 92 being positioned before the optical element 87.

FIG. 23 shows a configuration similar to that of FIG. 22, but shows alight transmission configuration using a spherical beam.

FIG. 24 shows a light reflection configuration using a parallel beam.

FIG. 25 shows a light reflection configuration using a spherical beam.

FIG. 26 shows a light reflection configuration using a parallel beam.The configuration of FIG. 26 comprises two screens 88.

FIG. 27 shows a light reflection configuration using a spherical beam.The configuration of FIG. 27 comprises two screens 88.

FIG. 28 shows a light reflection configuration with a small light beammoving on the lens. The configuration of FIG. 28 includes a beamsplitter 160, positioned between the light source 90 and the opticalelement 87. The beam splitter 160 is operative to split the light beamand direct the portion of the light beam which reflected from theoptical element 87 toward the camera 89. This is desirable because thelight path to and from the optical element 87 is thus kept close to theoptical axis of the optical element 87, so that the light follows acommon optical path.

It is appreciated that the configurations of FIGS. 24-27 may similarlyincorporate a beam splitter.

Reference is now made to FIG. 29, which is a simplified pictorialillustration of a cylinder map of a progressive lens, as produced by theapparatus of FIGS. 17A and 17B. The cylinder map of FIG. 29 comprisescylinder isopower lines 165, as are well known in the ophthalmic art. Itis appreciated that the apparatus of FIGS. 17A and 17B, and of FIGS.21-28, is capable of producing a wide variety of different outputsindicating measurements performed on the optical element 87. FIG. 29 ispresented by way of example only.

It is appreciated that there are a number of alternative configurationsof the apparatus of the present invention. The configurations describedabove are described by way of example only, and are not intended to belimiting.

It is appreciated that the software components of the present inventionmay, if desired, be implemented in ROM (read-only memory) form. Thesoftware components may, generally, be implemented in hardware, ifdesired, using conventional techniques.

It is appreciated that various features of the invention which are, forclarity, described in the contexts of separate embodiments may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment may also be provided separately or in anysuitable subcombination.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present invention isdefined only by the claims that follow:

We claim:
 1. Apparatus for mapping an optical element, the apparatuscomprising:a light source arranged to transmit a light beam toward theoptical element, a beam separator including a plurality of beamseparating elements which are operative to separate the light beam intoa corresponding plurality of light beam portions including at leastfirst and second light beam portions which may be distinguished from oneanother; an optical sensing device operative to generate a light spotmap including a plurality of light spots corresponding to said pluralityof beam separating elements, each light spot comprising an intersectionbetween a corresponding light beam portion and a plane disposed withinthe field of view or the optical sensing device; and an optical elementcharacteristic computation device operative to derive at least onecharacteristic of each of at least two locations within the opticalelement from said light spot map and including apparatus for identifyingthe beam separating element corresponding to an individual spot based atleast partly on distinguishing said first and second light beam portionfrom each other.
 2. Apparatus according to claim 1, wherein said lightspot map comprises a digital light spot map.
 3. Apparatus according toclaim 1, wherein said light spot map comprises an analog light spot map.4. Apparatus according to claim 1, wherein said beam separator comprisesan LCD (liquid crystal device).
 5. Apparatus according to claim 1,wherein said beam separator comprises an array of microlenses. 6.Apparatus according to claim 1, wherein said beam separator comprises ahole plate.
 7. Apparatus according to claim 1, wherein said opticalsensing device comprises a CCD camera.
 8. Apparatus according to claim1, wherein said optical sensing device comprises an IR camera. 9.Apparatus according to claim 1, wherein said optical sensing devicecomprises a photographic film.
 10. Apparatus according to claim 1,wherein said optical sensing device comprises a PSD (position sensordetector).
 11. Apparatus according to claim 1, wherein the light sourcecomprises a point source.
 12. Apparatus according to claim 1, whereinthe light source comprises a coherent light source.
 13. Apparatusaccording to claim 12, wherein said coherent light source comprises alaser source.
 14. Apparatus according to claim 1, wherein the lightsource comprises a noncoherent light source.
 15. Apparatus according toclaim 14, wherein said noncoherent light source comprises one of thefollowing:a tungsten light source; and a halogen light source. 16.Apparatus according to claim 1, wherein said apparatus for identifyingalso employs information regarding the location of the spot to identifya beam separating element corresponding to an individual spot. 17.Apparatus according to claim 1, wherein said light source comprises aparallel light source operative to transmit parallel light toward theoptical element.
 18. Apparatus according to claim 1, wherein said lightsource comprises a convergent light source operative to transmitconverging light toward the optical element.
 19. Apparatus according toclaim 1, wherein said light source comprises a divergent light sourceoperative to transmit diverging light toward the optical element. 20.Apparatus according to claim 1, wherein said computation device isoperative to derive at least one local characteristic of the opticalelement.
 21. Apparatus according to claim 11, and also comprising a beamsplitter positioned between the light source and the optical elementwhich is operative to split the light beam as it returns from theoptical element toward the optical sensing device.
 22. Apparatusaccording to claim 1, wherein said optical sensing device is on one sideof the optical element and said light source is on the other side of theoptical element.
 23. Apparatus according to claim 1, wherein the atleast one characteristic of the optical element comprises at least onecharacteristic of only one surface of the optical element.
 24. Apparatusaccording to claim 1, wherein said plurality of beam separating elementsincludes at least first and second beam separating elements withdifferent transmission properties.
 25. Apparatus according to claim 24,wherein said first beam separating element comprises an element whichabsorbs a portion of the beam.
 26. Apparatus according to claim 1wherein said plurality of beam separating elements includes an array ofbeam separating elements in which at least one individual beamseparating element is missing.
 27. Apparatus according to claim 26wherein said missing individual beam separating element is disposedsubstantially in the middle of the array.
 28. Apparatus according toclaim 1 wherein the light beam travels along a path extending from thelight source, through the beam separator and the optical element, to theoptical sensing device.
 29. A method for mapping a multifocal ophthalmicelement, the method comprising:illuminating a multifocal ophthalmicelement with a light beam; providing a first plurality of beamseparating elements operative to separate the light beam into acorresponding first plurality of light beam portions; generating adigital light spot map including a first plurality of light spotscorresponding to said first plurality of beam separating elements; andfor each of a second plurality of locations within the ophthalmicelement, deriving at least one multifocal ophthalmic element locationcharacteristic.
 30. A method according to claim 29, wherein saidophthalmic element comprises an ophthalmic lens.
 31. A method accordingto claim 29, wherein said ophthalmic element comprises an ophthalmicmold.
 32. A method according to claim 30, wherein said ophthalmic lenscomprises a contact lens.
 33. A method according to claim 32, whereinsaid contact lens comprises a hard contact lens.
 34. A method accordingto claim 32, wherein said contact lens comprises a soft contact lens.35. A method according to claim 34, wherein said soft contact lens isimmersed in a solution.
 36. A method according to claim 30, wherein saidophthalmic lens comprises an intraocular lens.
 37. A method according toclaim 29, wherein the at least one ophthalmic element characteristiccomprises at least one ophthalmic characteristic of only one surface ofthe ophthalmic element.
 38. A method for mapping a soft contact lenselement, the method comprising:illuminating a soft contact lens elementwith a light beam; providing a first plurality of beam separatingelements operative to separate the light beam into a corresponding firstplurality of light beam portions; generating a digital light spot mapincluding a first plurality of light spots corresponding to said firstplurality of beam separating elements; and for each of a secondplurality of locations within the lens element, deriving at least onesoft contact lens element location characteristic.
 39. A methodaccording to claim 38, wherein said soft contact lens element isimmersed in a solution.
 40. Apparatus for mapping an ophthalmic lens,the apparatus comprising:a light source arranged to transmit lighttoward the ophthalmic lens; a beam separator including a plurality ofbeam separating elements operative to separate a light beam into acorresponding plurality of light beam portions; an optical sensingdevice operative to generate a digital light spot map including aplurality of light spots corresponding to said plurality of beamseparating elements, each light spot comprising an intersection betweena corresponding light beam portion and a plane disposed within the fieldof view of the optical sensing device; and an ophthalmic characteristicmap generating device operative to generate a map of an ophthalmiccharacteristic of the ophthalmic lens based on said light spot map. 41.Apparatus according to claim 40, wherein said ophthalmic characteristicmap comprises an astigmatism map.
 42. Apparatus according to claim 40,wherein said ophthalmic characteristic map comprises an axis map. 43.Apparatus according to claim 40, wherein said ophthalmic characteristicmap comprises a tilt map.
 44. Apparatus according to claim 40, whereinsaid ophthalmic characteristic map comprises a curvature radius map. 45.A method for mapping an IR optical element, the methodcomprising:illuminating an IR optical element with a light beam;providing a first plurality of beam separating elements operative toseparate the light beam into a corresponding first plurality of lightbeam portions; generating a digital light spot map including a firstplurality of light spots corresponding to said first plurality of beamseparating elements; and for each of a second plurality of locationswithin the IR optical element, deriving at least one IR optical elementlocation characteristic.
 46. A method according to claim 45, wherein theat least one IR optical element characteristic comprises at least one IRoptical element characteristic of only one surface of the IR opticalelement.
 47. Apparatus for mapping a multifocal ophthalmic elementcomprising:a light source for illuminating a multifocal ophthalmicelement; a first plurality of beam separating elements operative toseparate a light beam into a corresponding first plurality of light beamportions; a digital light spot map generator operative to generate afirst plurality of light spots corresponding to said first plurality ofbeam separating elements, each light spot comprising an intersectionbetween a corresponding light beam portion and a plane disposed withinthe field view of the optical sensing device; and an ophthalmic elementlocation characterizer operative to derive at least one multifocalophthalmic element location characteristic, for each of a secondplurality of locations within the ophthalmic element.
 48. Apparatusaccording to claim 47, and also comprising:an aberration polynomialcomputation device operative to derive an aberration polynomialcharacterizing the ophthalmic element from said light spot map. 49.Apparatus for mapping an optical element, the apparatus comprising:alight source arranged to transmit a light beam toward the opticalelement; a beam separator including a plurality of beam separatingelements operative to separate a light beam arriving from the lightsource into a corresponding plurality of light beam portions beforeimpingement of the light beam on the optical element; an optical sensingdevice operative to generate a digital light spot map including aplurality of light spots corresponding to said plurality of beamseparating elements, each light spot comprising an intersection betweena corresponding light beam portion and a plane disposed within the fieldof view of the optical sensing device; and an optical elementcharacteristic computation device operative to derive at least onecharacteristic of each of at least two locations within the opticalelement from said light spot map.
 50. Apparatus according to claim 49,wherein the at least one characteristic of the optical element comprisesat least one characteristic of only one surface of the optical element.